In an imaging apparatus such as a digital video and a digital camera, a subject image is formed on an imaging element such as a CCD or a CMOS through a lens, whereby a subject is converted into two-dimensional image information. A camera module to be mounted on such an imaging apparatus is required to be small and thin.
In order to realize a small and thin camera module, a compound eye camera module has been proposed.
One example of the compound eye camera module is described in Patent Document 1, and will be described with reference to FIG. 13. A lens array 100 including three lenses 100a, 100b, and 100c and an imaging element 105 are placed so as to oppose each other. An optical filter array 102 having a green spectral filter 102a, a red spectral filter 102b, and a blue spectral filter 102c is provided on a surface of the lens array 100 on a subject side so that the green spectral filter 102a, the red spectral filter 102b, and the blue spectral filter 102c correspond to the three lenses 100a, 100b, and 100c, respectively. An optical filter array 103 having a green spectral filter 103a, a red spectral filter 103b, and a blue spectral filter 103c is provided also on a surface of the imaging element 105 on the lens array 100 side so that the green spectral filter 103a, the red spectral filter 103b, and the blue spectral filter 103c correspond to the three lenses 100a, 100b, and 100c, respectively. On the subject side of the optical filter array 102, a diaphragm member 107 having apertures (openings) at positions matched with optical axes of the lenses 100a, 100b, and 100c is placed. The lenses 100a, 100b, and 100c form subject images respectively on corresponding imaging regions on the imaging element 105. The wavelengths of light to be received by the lenses 100a, 100b, and 100c, respectively, are limited, so that they can form subject images on the imaging element 105 although they are single lenses. Thus, a camera module can be made thinner.
However, in the camera module, in order to prevent light having passed through a lens from being incident upon an imaging region not corresponding to the lens on the imaging element 105, the optical filter array 102 is provided between the diaphragm member 107 and the lens array 100, and furthermore, the optical filter array 103 is provided between the lens array 100 and the imaging element 105. Since a required optical length must be maintained between the lens array 100 and the imaging element 105, even if the optical filter array 103 is provided therebetween, the thickness of a lens module does not increase. However, when the optical filter array 102 is provided between the diaphragm member 107 and the lens array 100, the thickness of a camera module increases by the thickness of the optical filter array 102. More specifically, the camera module in FIG. 13 has a problem that thinning is insufficient.
A compound eye camera module solving the above problem is described in Patent Document 2, and will be described with reference to FIG. 14. A diaphragm member 111, a lens array 112, a light shielding block 113, an optical filter array 114, and an imaging element 116 are placed in this order from a subject side. The lens array 112 has a plurality of lenses. The diaphragm member 111 has apertures (openings) at positions matched with optical axes of the respective lenses of the lens array 112. The optical filter array 114 includes a plurality of optical filters having spectral characteristics that vary depending upon the region corresponding to each lens of the lens array 112, and covers a light receiving plane of the imaging element 116. The light shielding block 113 includes light shielding walls 113a at boundaries between adjacent lenses of the lens array 112, i.e., at positions matched with the boundaries between the adjacent optical filters of the optical filter array 114. The imaging element 116 is mounted on a semiconductor substrate 115. On the semiconductor substrate 115, a driving circuit 117 and a signal processing circuit 118 further are mounted.
According to the camera module, light having passed through a lens is prevented from being incident upon a filter of the optical filter array 114 not corresponding to the lens by the light shielding walls 113a of the light shielding block 113. Thus, the optical filter array 102 between the diaphragm member 107 and the lens array 100, which used to be required in the camera modules in FIG. 13, is not required. This enables the camera module to be thinned further.    Patent Document 1: JP 2001-78217 A    Patent Document 2: JP 2003-143459 A